The Wi-Fi Alliance Peer-to-Peer (P2P) Specification, also known as “Wi-Fi Direct,” allows for pre-association service discovery among peer devices. This protocol enables a client device or station (STA) to query peer STAs within Wi-Fi range to determine what services, if any, are provided by the peer STAs. Examples of such services may include: printing, gaming, file sharing, and/or Internet gateway services. Determining the services provided by peer STAs typically requires at least two phases of communications: a device discovery phase, followed by a service discovery phase.
During the device discovery phase, a client STA (e.g., a STA requesting a particular P2P service) determines the identity and/or availability of other STAs within Wi-Fi communication range. The client STA typically does this by “scanning” the 3 social channels (e.g., channels 1, 6, and 11 in the 2.4 GHz band) for incoming beacon frames and/or by broadcasting probe request frames to any STAs that may be listening on those channels. Thereafter, during the service discovery phase, the client STA queries the available peer STAs (discovered during the device discovery phase) about the services they provide. The client STA typically transmits service discovery requests to each peer STA that supports the service discovery operation, one at a time, until the client STA identifies a peer STA that provides the requested service.
Thus, during the service discovery phase, the client STA often queries several peer STAs (some of which may not provide any P2P services) before identifying a peer STA that provides the requested service. This is because the client STA is typically unaware of which services (if any) each of the peer STAs provides until after the service discovery phase. Furthermore, the client STA typically has no knowledge of whether the services provided by previously discovered peer STAs have changed unless it periodically repeats the service discovery operation (and device discovery operation) with each peer STA. Thus, a substantial amount of time and resources may be consumed in finding a peer STA that provides a desired service.